The Ames' test is the most widely-used genotoxicity assay and is required by regulatory agencies for the registration and approval of new chemicals. This assay is performed in Salmonella, but is considered a good indicator of genotoxicity for mammalian systems, because DNA damage and repair mechanisms are conserved between bacteria en humans. Indeed, the Ames' test exhibits the highest sensitivity for detection of carcinogenesis in rodents of all standard genotoxicity tests.
The Ames' Test is a mutation reversion test. The specific reversion site is an inactivating mutation in an amino acid biosynthesis operon. Mutagenesis is detected as growth in the presence of limiting amounts of the relevant amino acid. The assay can be performed on solid plates (Ames' plate incorporation test) or in liquid version (Ames' fluctuation assay). The main problem is the large amount of compound required. Even the miniaturized versions of Ames: mini-Ames (solid), and Ames II and MPF (liquid), require >10 mg amounts of test compound, which limits the use of this assay to detect mutagenic activity during early stages of drug discovery (when typically little amount of compound is available) or in complex mixtures of compounds, (where the active compound may be a small fraction of the total). The required sample amount also limits the ability for biomonitoring environmental mutagens in typical environmental mixtures
The present invention is based on the same principles as Ames test but is far more sensitive and provides quantitative information. The inventors have developed a novel method for detection of chemical mutagenesis that requires only a fraction of the sample used in Ames (at least 100-fold less). The present method can be used for drug discovery and for environmental biomonitoring. Also it may be used to screen high-yield natural products libraries for compounds targeting DNA as potential antimicrobial, anti-inflammatory or antitumor agents.